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Fingerboard and Nut Intersection

Discussion in 'Setup & Repair [DB]' started by iPlay15151515, Apr 4, 2005.


  1. Should the point where the fingerboard and nut intersect form a nearly perfect 90 degree angle? Not withstanding the curvature in the fingerboard to provide for the "scoop", it would seem that if the fingerboard is on a horizontal plane, then the edge of the nut where it joins the fingerboard should be on a vertical plane.

    When I pinch my strings to the fingerboard about 1 inch from the nut and also just below the neck body joint, I can see a uniform concave "scoop" with the string being approximately 2 mm above the fingerboard in the center between the pinch points.

    However, when I move the nut end pinch point toward the nut, this 2 mm gap quickly becomes 4 mm. It is as if my fingerboard wasn't planed with the same "scoop" contour on the final/top inch of the fingerboard as on the remainder of the board. The rate of change of the "scoop" contour is much greater in the final inch of the finger board at the nut end.

    After reading a number of posts on this and other forums, my initial conclusion is the bottom of the nut grooves should be on the same relative plane as the fingerboard at the intersection, with the fingerboard being approximately 2 business cards lower or offset from the nut grooves. Is this correct or do I have a distorted image of this relationship and/or the fingerboard profile?
     
  2. M_A_T_T

    M_A_T_T

    Mar 4, 2004
    Canada
    Is my picture an accurate depiction of your problem (though greatly exaggerated)? My upright bass experience is limited, but it sounds like the fingerboard may have been dressed without removing the nut. I would say no, this is not how it should be, because you won't be able to get your nut slots as low as if this area were planed in a relative plane to the rest of the fingerboard.
     

    Attached Files:

  3. Even though that looks a little exaggerated, MATT, that is very similar to the cut on my Lidyl. It has occured to me that this may be a dressing for gut strings, which tend to clatter more freely and need the extra room. In another thread, I recommended Mark Richard as having relocated to Asheville. Have you been able to find him, iplay4(15)?
     
  4. Matt-

    Thank you.

    Your drawing is exactly what I'm asking about. My bass is a second hand CCB that was purchased new about 5 years ago and was never played very much. I don't think the fingerboard has been altered since it left the factory. Both ends of the fingerboard have some degree of a "ski jump".

    The problem you described about the nut slots is the reason I posted the question. My string height, about .75 in from the nut, is too high to satisify me, and I feel like the "upturn" of the fingerboard at the nut is part of the problem.

    The problem of the "upturn" at the bridge end of the fingerboard seems easy enough to solve.

    I installed Supernil strings a little over a week ago, and I also need to widen the nut slots. The bass came with smooth steel string, and now the Supernills tune in small steps that are proportional to the space between the windings.

    I am still in the information gathering mode prior to bringing out the sandpaper, scrapers, planes, belt sander, router, disc grinder (just kidding about the last three).

    ________________

    Silver- I haven't found Mark Richard yet. Do you know how to contact him?
     
  5. Silver --

    I pulled this over from the Traeger General Thread so that I didn't continue hijacking the thread.



    When I clamp my D string to the fingerboard at a point .75 in. below the nut and also at a point 1.5 in from the bridge end, using a back light, the scoop appears symmetrical from clamp point to clamp point. The string is approximately .135 in above the fingerboard at the mid point between the clamping points.

    If I understand your post correctly, the above should be true when the clamp points are located at each end of the fingerboard.

    When I move the clamp points as close to the ends of the fingerboard as possible, the scoop no longer appears to be symmetrical and the string, at the maximum point, is approximately .460 in. above the fingerboard. The fingerboard is 33.25 in. long and the .460 is measured at 21 in. below the nut. This seems to indicate that I have high spots at both ends of my fingerboard with the bridge end being the highest.

    My understanding of the purpose of scoop is to reduce and/or eliminate string buzz. The scoop causes the fingerboard to "fall away" from the string where it makes contact and provides additional room for the string to vibrate without coming in contact with the fingerboard and buzzing.

    The above seems logical at least at 2 AM, but what happens when the string contacts the fingerboard at or below mid point of the scoop? It would appear that the scoop no longer "falls away" from the string but moves closer to the string.

    On my bass, this should be about 16.5 in. below the nut which is currently beyond my normal playing range.

    I can see how the angle the string makes with the fingerboard increases as the point of contact moves down the fingerboard so my guess is the need for scoop is less at the lower end.

    All of this makes me wonder if the concepts presented in "Zen And The Art Of Motorcycle Maintenance" also apply to the bass.
     
  6. Yes, that is what I'm saying. Your fingerboard and mine are of similar dimensions.

    Agreed. Making direct comparisons to my FB, the max on mine is about a quarter inch, which is still way too much.

    As the string stop gets shorter (moving away from the nut), the amplitude of the strings motion decreases as the vibrating length decreases, and less "fall away" room is required to prevent string noise. It appears that even at 2:00 AM, you have a good grasp of this. You've done some good practical analysis. In a case where there is way too much scoop and it is uneven as yours is, the affect when stopping notes above the max scoop point could almost cause the string to lie flat on the FB, depending on your bridge height. Do you have bridge adjusters? It would help in the final set-up after getting the FB planed down. My thought is that you will get more mileage and have to do less planing if you work at the nut end (plane it down) and then raise the bridge a little, since most of your playing is closer to the nut. How much to take off depends on first how much there is and then how much needs to be taken off. I'd go real slow and when you get the nut end reasonable, then start taking some from both ends. If you have that much room at the 21 in (near the octave stop), then you have a serious amount of wood to remove in any case. It will depend also on your plucking style and what angle you pull the strings. Some folks pull across, some out, and others sort of down and back so check as you go.

    My solution to this same aggravation is to get a new FB and start over. I have some kind of mystery wood FB currently and I think ebony will be a major improvement. But I'm sort of doing what I would call a full 100,000 mile overhaul.

    You know, I have that book, and I should re-read it. Patience and observation are everything necessary.
     
  7. Thanks to all of those who have posted answers to my questions about fingerboards and others who have posted on related topics, I decided my CCB fb was going to have the ski jump ends removed.

    Using a piece of open grid wall board sandpaper and my palm sander with 120 grit paper, I was able to easily remove the ebonized coating in about 30 minutes.

    This of course revealed several defects/patches in the wood as expected, but fortunately they are small and located near the south end of the fb.

    Not wanting to invest in special wood planes and scrapers, I located a mayonnaise jar with a nice curve and by applying several strategic taps with a ball peen hammer, I soon had some very sharp curved scrapers.

    Using the glass scrapers and a 2' carpenters square as a straight edge, I carefully scraped away the problems areas at each end of my fb. After about 45 minutes of scraping, sanding and measuring, I was satisfied with the results. The scoop remains very consistent from end to end and the ski jumps are gone.

    Using 120 grit sand paper wrapped around various sizes of drill bits, I was then able to cut my nut slots deeper to where I now have about 2+ business cards of clearance between the neck and strings at the nut end. After a little sanding on the nut top, the slots were back to a depth of about 1/2 the string diameter.

    The entire fb was finish sanded with 250 grit and 400 grit to the smoothness of a baby's bottom.

    The same drill bits and sandpaper were used to cut the slots in the bridge deeper in order to lower the strings to the desired height on the bridge end of the fb.

    Once I was satisfied with the slot depth/string height, I carefully sanded the bridge top to where the slot depth was slightly less then 1/2 the string diameter.

    Graphite was applied to both the nut slots and bridge slots before restringing, tuning and playing.

    The results were very satisfying even though the sound is still that of a CCB, and I didn't make any significant jumps on Sam's GT meter. The uniform and lower string height has certainly improved the plucker factor, and my left hand may now return to a normal size. The stops are much easier now which has and will continue to help with the intonation, but it's still a CCB. For now, all I need is something I can load in the back of my pickup and take to outdoor bluegrass events and the CCB seems to be working until I can find a carved bass at a steal. Did I mention that I squeak when I walk.


    Tomorrow, it's a trip to the shoe shop for some black shoe dye and the final finishing.


    As a final note:

    With every CCB comes a cCb (cheap chinese bridge) and mine is no exception. The bridge is bent and needs replacing soon.

    I emailed Bob Gollihur and asked him to email a copy of the instructions for fitting his adjustable bridge. After reading his clear and concise one page treatise on the subject, I'm certain that I'll be ordering one of his adjustable bridges in the near future.

    Thanks again to everyone who provided instruction and guidence to me on this project.